Two user equipments (UEs), such as e.g. mobile phones or laptops that are communicating using some kind of wide area access technology, such as e.g. a technology based on Long Term Evolution (LTE) or Ethernet are typically also capable of establishing communication via a common “short range” communication technology, such as e.g. Bluetooth, a special LTE “direct mode” or a Wireless Local Area Network (WLAN). In case the two UEs are located geographically close to each other, i.e. within radio range, it may be more beneficial to enable direct terminal-to-terminal communication using the mentioned short range communication interface, than to continue to communicate via the wide area access technology. By providing the option to use direct mode communication whenever the conditions are favorable enough, the network currently serving the UEs may be off-loaded, which may lead to the user getting lower charging and/or the UEs may obtain a higher bandwidth and/or a lower battery consumption.
The wide area access technology may typically be an LTE Radio Access Network (RAN) connected to 3GPP EPS, where the communication services are based on IMS, or any other type of suitable realization. The common short range technology may typically be a specially developed “LTE direct mode”, or, WLAN, but also other short range technologies may be used.
The TETRA system can start a direct mode session on user request. This is thus from networking point of view a completely new session and not a handover of an existing one.
In known use cases, two users may in general not be aware that they are close to each other. Even the network may be unaware of the fact that the UEs are located close to each other since the users may be subscribers of different operators. Conversely, even if the users are aware of their mutual close locations it is not obvious that switching from a network connection to a direct mode is beneficial, e.g. the radio conditions or charging conditions may still be unfavorable.
In addition, there are user privacy problems by using beacons with global and/or traceable identifiers, such as WLAN BSSID/SSID or Bluetooth Device Name.